feat: add dodge roll mechanic (closes #338)

code/datums/components/dodge.dm

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+/// Dodge roll mechanic: while dodging, the mob takes no damage.
+/datum/component/dodge
+	/// How long (deciseconds) the dodge i-frames last.
+	var/dodge_duration = 5
+	/// Cooldown (deciseconds) before the mob can dodge again.
+	var/dodge_cooldown = 30
+	/// Whether the mob is currently mid-dodge (invulnerable).
+	var/dodging = FALSE
+	/// World time at which the mob can dodge again.
+	var/next_dodge = 0
+
+/datum/component/dodge/Initialize(duration = 5, cooldown = 30)
+	if(!isliving(parent))
+		return COMPONENT_INCOMPATIBLE
+	dodge_duration = duration
+	dodge_cooldown = cooldown
+	RegisterSignal(parent, COMSIG_MOB_APPLY_DAMAGE, PROC_REF(on_apply_damage))
+	return ..()
+
+/datum/component/dodge/Destroy(force, silent)
+	UnregisterSignal(parent, COMSIG_MOB_APPLY_DAMAGE)
+	return ..()
+
+/datum/component/dodge/proc/on_apply_damage(mob/living/source, damage, damagetype, def_zone, blocked, wound_bonus, bare_wound_bonus, sharpness, attack_direction, attacking_item)
+	SIGNAL_HANDLER
+	if(dodging)
+		return COMPONENT_NO_DAMAGE
+
+/// Triggers a dodge roll. Returns TRUE if the dodge started.
+/datum/component/dodge/proc/start_dodge()
+	if(dodging || (world.time < next_dodge))
+		return FALSE
+	var/mob/living/L = parent
+	dodging = TRUE
+	L.visible_message(span_danger("[L] performs a dodge roll!"))
+	// brief movement flair: nudge the mob in its facing direction
+	if(L.dir)
+		step(L, L.dir)
+	addtimer(CALLBACK(src, PROC_REF(end_dodge)), dodge_duration)
+	return TRUE
+
+/datum/component/dodge/proc/end_dodge()
+	dodging = FALSE
+	next_dodge = world.time + dodge_cooldown
+
+/// Verb so players can bind a key to dodge.
+/mob/living/verb/dodge()
+	set name = "Dodge Roll"
+	set category = "IC"
+	set desc = "Perform a dodge roll, briefly avoiding all damage."
+	var/datum/component/dodge/D = src.GetComponent(/datum/component/dodge)
+	if(!D)
+		D = src.AddComponent(/datum/component/dodge)
+	if(D)
+		to_chat(src, D.start_dodge() ? span_notice("You dodge roll!") : span_warning("You can't dodge yet!"))

html/changelogs/changelog_dodge.yml

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+- type: add
+  id: dodge_roll
+  author: harshaaaaw
+  message: Added a dodge roll mechanic — players can perform a dodge roll that briefly avoids all incoming damage, with a short cooldown.
+  changes:
+    - add: Players can now perform a dodge roll (IC verb) that grants brief damage immunity.